Process for the removal of hydrocarbonaceous compounds from an aqueous stream and hydrogenating these compounds

ABSTRACT

A process for the removal of hydrocarbonaceous compounds from an aqueous feed stream comprising less than about 1 volume percent of the hydrocarbonaceous compounds which comprises the steps of: (a) contacting the aqueous stream with an adsorbent to remove the hydrocarbonaceous compounds from the aqueous stream to provide an aqueous stream having a reduced concentration of hydrocarbonaceous compounds; (b) contacting spent adsorbent which has accumulated the hydrocarbonaceous compounds from the aqueous stream with an elution solvent to remove the hydrocarbonaceous compounds from the spent adsorbent thereby regenerating the adsorbent; (c) contacting the elution solvent in admixture with the hydrocarbonaceous compounds which were removed from the spent adsorbent in step (b) in the presence of hydrogen with a hydrogenation catalyst in a hydrotreating reaction zone; (d) contacting the hydrotreating reaction zone effluent with an aqueous scrubbing solution; and (e) introducing a resulting admixture of the reaction zone effluent and the aqueous scrubbing solution into a separation zone to provide a hydrotreated elution solvent and a spent aqueous stream having a volume of less than about 4% of the aqueous feed stream.

CROSS REFERENCE TO RELATED APPLICATION

This application is a continuation-in-part of U.S. application Ser. No.791,646 filed Oct. 28, 1985, now U.S. Pat. No. 4,661,256 the teachingsof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The field of art to which this invention pertains is the removal oftrace quantities of hydrocarbonaceous compounds from an aqueous stream.More particularly, the invention relates to the removal of tracequantities of hydrocarbonaceous compounds which are hazardous orotherwise obnoxious. More specifically, the invention relates to aprocess for the removal of hydrocarbonaceous compounds from an aqueousfeed stream comprising less than about 1 volume percent of thehydrocarbonaceous compounds which comprises the steps of: (a) contactingthe aqueous stream with an adsorbent to remove the hydrocarbonaceouscompounds from the aqueous stream to provide an aqueous stream having areduced concentration of hydrocarbonaceous compounds; (b) contactingspent adsorbent which has accumulated the hydrocarbonaceous compoundsfrom the aqueous stream with an elution solvent to remove thehydrocarbonaceous compounds from the spent adsorbent therebyregenerating the adsorbent; (c) contacting the elution solvent inadmixture with the hydrocarbonaceous compounds which were removed fromthe spent adsorbent in step (b) in the presence of hydrogen with ahydrogenation catalyst in a hydrotreating reaction zone; (d) contactingthe hydrotreating reaction zone effluent with an aqueous scrubbingsolution; and (e) introducing a resulting admixture of the reaction zoneeffluent and the aqueous scrubbing solution into a separation zone toprovide a hydrotreated elution solvent and a spent aqueous stream havinga volume of less than about 4% of the aqueous feed stream.

INFORMATION DISCLOSURE

In U.S. Pat. No. 3,919,398 (Davis), a method is disclosed for recoveringbromine as hydrogen bromide from aromatic bromides. The method involvesreacting the aromatic bromide with hydrogen at a temperature within therange from about 200° to about 600° C. in the presence of a palladiumactivated catalyst.

In U.S. Pat. No. 3,892,818 (Scharfe et al), a method is disclosed forthe conversion of hydrocarbon chlorides in the presence of hydrogen tohydrocarbons and hydrogen chloride wherein the process takes place in agaseous phase and in the presence of a rhodium-containing catalyst.

In U.S. Pat. No. 4,201,665 (Savage et al), a method is disclosed for theuse of nonstoichiometric carbon-sulfur compounds to remove a widevariety of organic and/or inorganic materials from liquids. The '665patent teaches that the removal of biorefractory organics, such asaromatics, is particularly effective and that the spent adsorbent maythen be regenerated. The '665 patent also teaches that organiccomponents subject to removal include, but are not limited to, aromaticcompounds, aliphatic compounds, phenolic compounds, organic acids,alcohols, esters, aldehydes, amines, pyridines, morpholines, esters,glycols, glycol ethers, halogenated hydrocarbons, ketones, oxides, vinylchloride and the like.

In U.S. Pat. No. 3,595,931 (Hay et al), a process is disclosed toreplace the halogen moiety on a halogenated aromatic with hydrogen bycontacting the halogenated aromatic in the vapor phase in the presenceof hydrogen with a supported catalyst containing a minor amount ofplatinum or palladium and a minor amount of a hydrated alkali oralkaline earth metal oxide such as potassium hydroxide.

In Kirk, Othmer, Encyclopedia of Chemical Technology, Third Edition,Volume 12, at page 999, a method is described to remove hydrogenchloride by scrubbing a gaseous mixture with water.

BRIEF SUMMARY OF THE INVENTION

The invention provides a process for the removal of hydrocarbonaceouscompounds from an aqueous feed stream comprising less than about 1volume percent of said hydrocarbonaceous compounds by contacting theaqueous feed stream with an adsorbent to remove said hydrocarbonaceouscompounds from the aqueous feed stream and whereby the spent adsorbentis regenerated by removal of accumulated hydrocarbonaceous compoundsfrom the adsorbent by means of an elution solvent and subsequentprocessing of these hydrocarbonaceous compounds in a hydrotreatingreaction zone. The resulting effluent from the hydrotreating reactionzone is contacted with an aqueous scrubbing solution. The process of thepresent invention thereby provides a decontaminated aqueous stream and aspent aqueous scrubbing solution having a volume of only, 4% or less ofthe original feed stream. Therefore, the quantity of contaminated wastewater has been greatly reduced and the residual spent aqueous scrubbingsolution contains dissolved inorganic species which solution may readilybe converted or discarded by means of convenient techniques known bythose skilled in the art. In the case where the hydrocarbonaceouscompounds are chlorinated hydrocarbons and the scrubbing solutioncontains sodium hydroxide, the resulting spent aqueous scrubbingsolution is an aqueous solution of sodium chloride which may, forexample, be reduced in volume by evaporation. The present invention alsocontemplates the recycle of hydrotreated elution solvent to a spentadsorbent for removal of hydrocarbonaceous compounds.

One broad embodiment of the invention may be characterized as a processfor the removal of hydrocarbonaceous compounds from an aqueous feedstream comprising less than about 1 volume percent of thehydrocarbonaceous compounds which comprises the steps of: (a) contactingthe aqueous stream with an adsorbent to remove the hydrocarbonaceouscompounds from the aqueous stream to provide an aqueous stream having areduced concentration of hydrocarbonaceous compounds; (b) contactingspent adsorbent which has accumulated the hydrocarbonaceous compoundsfrom the aqueous stream with an elution solvent to remove thehydrocarbonaceous compounds from the spent adsorbent therebyregenerating the adsorbent; (c) contacting the elution solvent inadmixture with the hydrocarbonaceous compounds which were removed fromthe spent adsorbent in step (b) in the presence of hydrogen with ahydrogenation catalyst in a hydrotreating reaction zone; (d) contactingthe hydrotreating reaction zone effluent with an aqueous scrubbingsolution; and (e) introducing a resulting admixture of the reaction zoneeffluent and the aqueous scrubbing solution into a separation zone toprovide a hydrotreated elution solvent and a spent aqueous stream havinga volume of less than about 4% of the aqueous feed stream.

Another embodiment of the invention may be characterized as a processfor the removal of hydrocarbonaceous compounds from an aqueous feedstream comprising less than about 1 volume percent of thehydrocarbonaceous compounds which comprises the steps of: (a) contactingthe aqueous stream with an adsorbent to remove the hydrocarbonaceouscompounds from the aqueous stream to provide an aqueous stream having areduced concentration of hydrocarbonaceous compounds; (b) contactingspent adsorbent which has accumulated the hydrocarbonaceous compoundsfrom the aqueous stream with an elution solvent to remove thehydrocarbonaceous compounds from the spent adsorbent therebyregenerating the adsorbent; (c) contacting the elution solvent inadmixture with the hydrocarbonaceous compounds which were removed fromthe spent adsorbent in step (b) in the presence of hydrogen with ahydrogenation catalyst in a hydrotreating reaction zone; (d) contactingthe hydrotreating reaction zone effluent with an aqueous scrubbingsolution; (e) introducing a resulting admixture of the reaction zoneeffluent and the aqueous scrubbing solution into a separation zone toprovide a hydrotreated elution solvent and a spent aqueous stream havinga volume of less than about 4% of the aqueous feed stream; and (f)recycling at least a portion of the hydrotreated elution solvent fromstep (e) to provide at least a portion of the elution solvent utilizedin step (b).

Other embodiments of the subject invention encompass further detailssuch as potential hydrocarbonaceous compound contaminants, aqueousscrubbing solutions, hydrotreating catalysts, adsorbents, elutionsolvents and operating conditions, all of which are hereinafterdisclosed in the following discussion of each of these facets of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing is a simplified process flow diagram of a preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

There is a steadily increasing demand for technology which is capable ofeliminating trace quantities of hydrocarbonaceous compounds from aqueousstreams such as waste water and potable water, for example. Once anorganic phase is decanted from a water phase, the remaining water maypotentially contain trace quantities of organic compounds such ashydrocarbonaceous compounds for example. Before waste water can bedischarged into the environment, these trace quantities ofhydrocarbonaceous compounds must be reduced or eliminated. In the eventthat these trace hydrocarbonaceous compounds are toxic, carcinogenic orotherwise obnoxious, it is preferred that the hydrocarbonaceouscompounds not only be removed from the aqueous phase but converted intoless noxious compounds. For purposes of this invention, less noxiouscompounds are defined as those compounds which may be recycled or soldin legitimate commerce. Therefore, those skilled in the art have soughtto find feasible techniques to remove trace amounts of hydrocarbonaceouscompounds from an aqueous phase. Although simple in concept,conventional liquid-liquid extraction often is not practical for theremoval of hydrocarbonaceous compound contaminants at theparts-per-million level or even lower concentrations.

The present invention provides an improved process for the removal oftrace quantities of hydrocarbonaceous compounds from an aqueous streamthereby increasing the quantity of decontaminated waste water. A widevariety of hydrocarbonaceous compounds are to be considered candidatesfor removal from an aqueous stream in accordance with the process of thepresent invention. Examples of compounds which are suitable fortreatment by the process of the present invention are halogenatedhydrocarbons. Certain halogenated hydrocarbons having demonstrated orpotential toxicity include but are not limited to kepone, halogenatedbiphenyls, halogenated cyclodienes, such as aldrin, dieldrin, andhexachlorocyclopentadienes, dibromochloropropane, halogenated phthalicanhydrides, such as polybromophthalicanhydride, tetrachloroethylene,polychlorodioxins such as tetrachlorodibenzodioxin, halogenated organicphosphates such as 2,2 dichlorovinyldimethyl phosphate. Additionalexamples of compounds which are suitable for treatment includeorganometallic compounds and especially those which contain metals suchas lead, mercury, cadmium, cobalt, arsenic, vanadium, and chromium.Contaminating hydrocarbonaceous compounds may comprise sulfur, oxygen,metal or nitrogen components. In accordance with the present invention,generally any hydrocarbonaceous compound may be removed from an aqueousstream. It is preferred that the trace quantities of hydrocarbonaceouscompounds are present in the aqueous stream in an amount less than about10,000 PPM (1 weight percent) and more preferably in an amount less thanabout 5,000 PPM (0.5 weight percent).

In accordance with the subject invention, an aqueous stream containingtrace quantities of hydrocarbonaceous compounds is contacted with asuitable adsorbent which selectively retains the trace hydrocarbonaceouscompounds and produces an aqueous stream with a reduced concentration ofhydrocarbonaceous compounds. Suitable adsorbents may be selected frommaterials which exhibit the primary requirement of hydrocarbonaceouscompound selectivity and which are otherwise convenient to use. Suitableadsorbents include, for example, molecular sieves, amorphoussilica-alumina gel, silica gel, activated carbon, activated alumina andclays. Of course, it is recognized that for a given case, a particularadsorbent may give better results than others.

The selected adsorbent is contacted with an aqueous stream containingtrace quantities of hydrocarbonaceous compounds in an adsorption zone.The adsorbent may be installed in the adsorption zone in any suitablemanner. A preferred method for the installation of the adsorbent is in afixed bed arrangement. The adsorbent may be installed in one or morevessels and in either series or parallel flow. The flow of an aqueousstream through the adsorption zone is preferably performed in a parallelmanner so that when one of the adsorbent beds or chambers is spent bythe accumulation of hydrocarbonaceous compounds thereon, the spentadsorbent zone may be bypassed while continuing uninterrupted operationthrough the parallel adsorbent zone.

During adsorption, the adsorption zone is preferably maintained at apressure from about atmospheric to about 1500 psig (10342 kPa gauge), atemperature from about 32° F. (0° C.) to about 300° F. (149° C.) and aliquid hourly space velocity from about 0.1 hr⁻¹ to about 500 hr⁻¹. Theflow of the aqueous stream containing trace quantities ofhydrocarbonaceous compounds through the adsorption zone may be conductedin an upflow, downflow or radial flow manner. The temperature andpressure of the adsorption zone are preferably selected to maintain theaqueous stream in the liquid phase. As used herein, the term"essentially hydrocarbon-free" connotes a hydrocarbonaceous compoundconcentration of less than about 10 PPM.

The spent zone of adsorbent is regenerated by isolating the spentadsorption zone and contacting the adsorbent with an elution solvent toremove the hydrocarbonaceous compounds thereby regenerating theadsorbent. In general, an elution solvent is utilized which possesses ahigh solvent selectivity towards the hydrocarbonaceous compoundsadsorbed on the adsorbent and which has no deleterious effect on theadsorbent. Preferred elution solvents comprise naphtha, kerosene, dieselfuel, gas oil or mixtures thereof. During regeneration of the adsorbent,the adsorption zone is preferably maintained at a pressure from aboutatmospheric to about 1500 psig (10342 kPa gauge), and a temperature fromabout 32° F. (0° C.) to about 300° F. (149° C.). The flow of the elutionsolvent through the adsorption zone during regeneration thereof may beconducted in an upflow, downflow or radial flow manner. The elutionsolvent during the regeneration of adsorbent may be present in a liquidphase or a gas-liquid mixed phase.

The resulting elution solvent containing the hydrocarbonaceous compoundsis introduced into a hydrotreating or hydrogenation zone and iscontacted with a hydrogen-rich gaseous phase and a hydrogenationcatalyst. The catalytic hydrogenation zone may contain a fixed, ebulatedor fluidized catalyst bed. This reaction zone is preferably maintainedunder an imposed pressure from about 100 psig (689 kPa gauge) to about2000 psig (13790 kPa gauge) and more preferably under a pressure fromabout 200 psig (1379 kPa gauge) to about 1800 psig (12411 kPa gauge).Suitably, such reaction is conducted with a maximum catalyst bedtemperature in the range of about 350° F. (177° C.) to about 850° F.(454° C.) selected to perform the desired conversion to reduce oreliminate the undesirable characteristics or components of thehydrocarbonaceous compounds. Further preferred operating conditionsinclude liquid hourly space velocities in the range from about 0.2 hr⁻¹to about 10 hr⁻¹ and hydrogen circulation rates from about 200 standardcubic feet per barrel (SCFB) (35.6 m³ /m³) to about 10,000 SCFB (1778 m³/m³), preferably from about 300 SCFB (53.3 m³ /m³) to about 8000 SCFB(1422 m³ /m³).

The preferred catalytic composite disposed within the hereinabovedescribed hydrogenation zone can be characterized as containing ametallic component having hydrogenation activity, which component iscombined with a suitable refractory inorganic oxide carrier material ofeither synthetic or natural origin. The precise composition and methodof manufacturing the carrier material is not considered essential to thepresent invention. Preferred carrier materials are alumina, silica andmixtures thereof. Suitable metallic components having hydrogenationactivity are those selected from the group comprising the metals ofGroups VI-B and VIII of the Periodic Table, as set forth in the PeriodicTable of the Elements, E. H. Sargent and Company, 1964. Thus, thecatalytic composites may comprise one or more metallic components fromthe group of molybdenum, tungsten, chromium, iron, cobalt, nickel,platinum, iridium, osmium, rhodium, ruthenium, and mixtures thereof. Theconcentration of the catalytically active metallic component, orcomponents, is primarily dependent upon a particular metal as well asthe physical and/or chemical characteristics of the particularhydrocarbon feedstock. For example, the metallic components of GroupVI-B are generally present in an amount within the range of from about 1to about 20 weight percent, the iron-group metals in an amount withinthe range of about 0.2 to about 10 weight percent, whereas the noblemetals of Group VIII are preferably present in an amount within therange of from about 0.1 to about 5 weight percent, all of which arecalculated as if these components existed within the catalytic compositein the elemental state. In addition, any catalyst employed commerciallyfor hydrotreating middle distillate hydrocarbonaceous compounds toremove nitrogen and sulfur should normally function effectively in thehydrogenation zone of the present invention.

The hydrocarbonaceous effluent from the hydrogenation zone is contactedwith an aqueous scrubbing solution and the resulting admixture isadmitted to a separation zone in order to separate a spent aqueousscrubbing solution having a volume of less than about 4% of the aqueousfeed stream, a hydrogenated hydrocarbonaceous phase comprisinghydrotreated elution solvent and hydrotreated hydrocarbonaceouscompounds which formerly contaminated the waste water feed stream and ahydrogen-rich gaseous phase. The contact of the hydrocarbonaceouseffluent from the hydrogenation zone with the aqueous scrubbing solutionmay be performed in any convenient manner and is preferably conducted byco-current, in-line mixing which may be promoted by inherent turbulence,mixing orifices or any other suitable mixing means. The aqueousscrubbing solution is selected depending on the characteristics of thehydrocarbonaceous compounds which are entrained in the contaminatedwaste water feed stream. For example, if the hydrocarbonaceous compoundspresent in the waste water feed stream comprise halogenated compounds,the aqueous scrubbing solution preferably contains a basic compound suchas calcium hydroxide, potassium hydroxide or sodium hydroxide in orderto neutralize the acid which is formed during the hydrogenation of thehalogen compounds. In the event that the hydrocarbonaceous compoundcontaminants contain only sulfur and nitrogen compounds, pure water is asuitable aqueous scrubbing solution. The resulting hydrotreatedhydrocarbonaceous phase is recovered and the hydrogen-rich gaseous phasemay be recycled to the hydrogenation zone if desired. In a preferredembodiment of the subject invention, at least a portion of the recoveredhydrocarbonaceous phase is recycled as at least a portion of the elutionsolvent mentioned hereinabove. A portion of the aqueous scrubbingsolution recovered in the separation zone may be recycled to contact thehydrocarbonaceous effluent from the hydrogenation zone. The spentaqueous scrubbing solution may be neutralized or otherwise treated toprovide a more environmentally acceptable effluent. Therefore, thevolume of contaminated waste water has been greatly reduced and theresidual spent aqueous scrubbing solution contains dissolved inorganicspecies which solution may readily be converted or discarded by means ofconvenient techniques known by those skilled in the art.

In the drawing, the process of the present invention is illustrated bymeans of a simplified flow diagram in which such details as pumps,instrumentation, heat-exchange and heat-recovery circuits, compressors,surge tanks and similar hardware have been deleted as beingnon-essential to an understanding of the techniques involved. The use ofsuch miscellaneous appurtenances are well within the purview of oneskilled in the art.

With reference now to the drawing, an aqueous feed stream contaminatedwith trace quantities of hydrocarbonaceous compounds is introduced intothe process via conduit 1 and is passed via conduit 2, valve 3 andconduit 4 into adsorption zone 5. Alternatively, the contaminated wastewater charge stock is introduced via conduit 6, valve 7, and conduit 8into adsorption zone 9 which is located in parallel with adsorption zone5. An aqueous stream having a reduced concentration of hydrocarbonaceouscompounds is removed from adsorption zone 5 via conduit 10, conduit 11,valve 12, conduit 13 and recovered. In the alternative, an aqueousstream having a reduced concentration of hydrocarbonaceous compounds isremoved from adsorption zone 9 via conduit 14, valve 15, conduit 16,conduit 13 and recovered. In the event adsorption zone 9 is to beregenerated, valves 7 and 15 are closed for isolation and an elutionsolvent is introduced via conduit 17, valve 20, conduit 17, and conduit14 into adsorption zone 9. An elution solvent rich in hydrocarbonaceouscompounds which have been extracted from adsorption zone 9 is removedvia conduit 8, conduit 21, valve 22 and conduit 21 and is introducedinto hydrotreating reaction zone 25. In the event that adsorption zone 5is to be regenerated, valves 3 and 12 are closed for isolation and anelution solvent is introduced via conduit 17, conduit 18, valve 19,conduit 18 and conduit 10 into adsorption zone 5. An elution solventrich in hydrocarbonaceous compounds is removed from adsorption zone 5via conduit 4, conduit 23, valve 24, conduit 23, and conduit 21 andintroduced into hydrotreating reaction zone 25. A hydrogen-rich gaseousstream which is derived in a manner hereinafter described is introducedvia conduit 32 and conduit 21 into hydrotreating reaction zone 25.Make-up hydrogen is introduced via conduit 33, conduit 32 and conduit 21into hydrotreating reaction zone 25. The admixture of elution solventand hydrocarbonaceous contaminants is hydrogenated in hydrotreatingreaction zone 25 in the presence of a hydrogenation catalyst maintainedat hydrogenation conditions as described hereinabove. The resultinghydrotreated elution solvent and hydrocarbonaceous compounds and agaseous phase are removed from hydrotreating reaction zone 25 viaconduit 26 and contacted with an aqueous scrubbing solution introducedvia conduit 27. The resulting mixture is introduced via conduit 26 intohigh pressure separator 28. A hydrogen-rich gaseous phase is removedfrom high pressure separator 28 via conduit 32 and recycled as describedhereinabove. A detoxified hydrocarbonaceous stream comprisinghydrotreated elution solvent is removed from high pressure separator 28via conduit 29 and recovered. At least a portion of the detoxifiedhydrocarbonaceous stream comprising hydrotreated elution solvent isrecycled via conduit 31 to provide at least a portion of the elutionsolvent which is provided via conduit 17. A spent aqueous scrubbingsolution is removed from high pressure separator 28 via conduit 30 andis recovered.

The process of the present invention is further demonstrated by thefollowing illustrative embodiment. This illustrative embodiment ishowever not presented to unduly limit the process of this invention, butto further illustrate the advantages of the hereinabove describedembodiments. The following data were not obtained by the actualperformance of the present invention, but are considered prospective andreasonably illustrative of the expected performance of the invention.

ILLUSTRATIVE EMBODIMENT

This illustrative embodiment describes the removal of poly chlorinatedbiphenyl (PCB) from an aqueous stream which contains 1 weight PPM of PCBin an adsorption zone, the subsequent elution of the PCB from anadsorbent contained in the adsorption zone and the conversion of theeluted PCB by hydrotreating to produce innocuous hydrocarbonaceouscompounds.

An aqueous stream of water containing 1 weight PPM of PCB is introducedinto an adsorption zone containing activated carbon particles atconditions including a temperature of about 100° F. (38° C.), a pressureof about 10 psig (69 kPa gauge), and a liquid hourly space velocity ofabout 10. The resulting aqueous phase is found to contain less than 1PPB of PCB. Another adsorption zone containing activated carbonparticles which is located in parallel with the hereinabove mentionedadsorption zone and is regenerated to remove previously adsorbed PCB bycontacting the activated carbon containing PCB with an elution solventcomprising heptane, a component of naphtha, at conditions which includea temperature of about 100° F. (38° C.), and a pressure of about 10 psig(69 kPa gauge) for a time sufficient to elute or remove substantiallyall of the transient PCB from the activated carbon adsorbent. Theresulting admixture of elution solvent and PCB removed from theadsorbent is then introduced together with a gaseous hydrogen-richstream into a hydrotreating reaction zone loaded with a catalystcomprising alumina, cobalt and molybdenum. The hydrotreating reaction isconducted with a catalyst peak temperature of 750° F. (399° C.), apressure of 900 psig (6205 kPa gauge), a liquid hourly space velocity of1 based on fresh feed and a hydrogen circulation rate of 2500 SCFB (444std m³ /m³). The effluent from the hydrotreating reaction zone iscontacted with an aqueous sodium hydroxide solution in an amount of 500volume percent based on the hydrocarbonaceous effluent from thehydrotreating zone or 0.0005 volume percent based on the aqueous feedstream. The admixture of the hydrotreating reaction zone effluent andthe aqueous scrubbing solution is introduced into a separation zone toprovide a spent aqueous stream and a hydrotreated elution solvent havingless than 1 PPM of PCB. By means of the present invention, the volume ofcontaminated water has been greatly reduced and the type of residualwaste water is deemed to be much easier to cope with than the aqueousfeed stream containing hydrocarbonaceous products.

The foregoing description, drawing and illustrative embodiment clearlyillustrate the advantages encompassed by the process of the presentinvention and the benefits to be afforded with the use thereof.

I claim as my invention:
 1. A process for the removal ofhydrocarbonaceous compounds from an aqueous feed stream comprising lessthan about 1 volume percent of said hydrocarbonaceous compounds whichcomprises the steps of:(a) contacting said aqueous stream with a solidadsorbent to remove said hydrocarbonaceous compounds from said aqueousstream to provide an aqueous stream having a reduced concentration ofhydrocarbonaceous compounds; (b) contacting spent adsorbent which hasaccumulated said hydrocarbonaceous compounds from said aqueous streamwith an elution solvent to remove said hydrocarbonaceous compounds fromsaid spent adsorbent thereby regenerating said adsorbent; (c) contactingsaid elution solvent in admixture with said hydrocarbonaceous compoundswhich were removed from said spent adsorbent in step (b) in the presenceof hydrogen with a hydrogenation catalyst in a hydrotreating reactionzone; (d) contacting the hydrotreating reaction zone effluent with anaqueous scrubbing solution; and (e) introducing a resulting admixture ofsaid reaction zone effluent and said aqueous scrubbing solution into aseparation zone to provide a hydrotreated elution solvent and a spentaqueous stream having a volume of less than about 4% of said aqueousfeed stream.
 2. The process of claim 1 wherein said hydrocarbonaceouscompounds comprise hazardous hydrocarbonaceous compounds.
 3. The processof claim 2 wherein said hazardous hydrocarbonaceous compounds arehalogenated hydrocarbons or organometallic compounds.
 4. The process ofclaim 1 wherein said hydrotreating reaction zone is operated atconditions which include a pressure from about 100 psig (689 kPa gauge)to about 2000 psig (13790 kPa gauge), a maximum catalyst temperaturefrom about 350° F. (177° C.) to about 850° F. (454° C.) and a hydrogencirculation rate from about 200 SCFB (35.6 std m³ /m³) to about 10,000SCFB (1778 std m³ /m³).
 5. The process of claim 1 wherein saidhydrogenation catalyst comprises a refractory inorganic oxide and atleast one metallic compound having hydrogenation activity.
 6. Theprocess of claim 5 wherein said metallic compound is selected from themetals of Groups VI-B and VIII of the Periodic Table.
 7. The process ofclaim 1 wherein said aqueous scrubbing solution comprises an alkalinecompound.
 8. The process of claim 7 wherein said alkaline compound issodium hydroxide, potassium hydroxide or calcium hydroxide.
 9. Theprocess of claim 1 wherein said adsorbent is silica gel, activatedcarbon, activated alumina, silica-alumina gel, clay, molecular sieves oradmixtures thereof.
 10. The process of claim 1 wherein said contactingconducted in step (a) is performed at conditions which include apressure from about atmospheric to about 1500 psig (10342 kPa gauge) anda temperature from about 32° F. (0° C.) to about 300° F. (149° C.) and aliquid hourly space velocity from about 0.1 hr⁻¹ to about 500 hr⁻¹. 11.The process of claim 1 wherein the adsorbent regeneration conducted instep (b) is performed at conditions which include a pressure from aboutatmospheric to about 1500 psig (10342 kPa gauge) and a temperature fromabout 32° F. (0° C.) to about 300° F. (149° C.).
 12. The process ofclaim 1 wherein said aqueous stream having a reduced hydrocarbonaceouscompound concentration is essentially hydrocarbon free.
 13. The processof claim 1 wherein said elution solvent is naphtha, kerosene, dieselfuel, gas oil or mixtures thereof.
 14. A process for the removal ofhydrocarbonaceous compounds from an aqueous feed stream comprising lessthan about 1 volume percent of said hydrocarbonaceous compounds whichcomprises the steps of:(a) contacting said aqueous stream with anadsorbent to remove said hydrocarbonaceous compounds from said aqueousstream to provide an aqueous stream having a reduced concentration ofhydrocarbonaceous compounds; (b) contacting spent adsorbent which hasaccumulated said hydrocarbonaceous compounds from said aqueous streamwith an elution solvent to remove said hydrocarbonaceous compounds fromsaid spent adsorbent thereby regenerating said adsorbent; (c) contactingsaid elution solvent in admixture with said hydrocarbonaceous compoundswhich were removed from said spent adsorbent in step (b) in the presenceof hydrogen with a hydrogenation catalyst in a hydrotreating reactionzone; (d) contacting the hydrotreating reaction zone effluent with anaqueous scrubbing solution; (e) introducing a resulting admixture ofsaid reaction zone effluent and said aqueous scrubbing solution into aseparation zone to provide a hydrotreated elution solvent and a spentaqueous stream having a volume of less than about 4% of said aqueousfeed stream; and (f) recycling at least a portion of said hydrotreatedelution solvent from step (e) to provide at least a portion of saidelution solvent utilized in step (b).
 15. The process of claim 14wherein said hydrocarbonaceous compounds comprise hazardoushydrocarbonaceous compounds.
 16. The process of claim 15 wherein saidhazardous hydrocarbonaceous compounds are halogenated hydrocarbons ororganometallic compounds.
 17. The process of claim 14 wherein saidhydrotreating reaction zone is operated at conditions which include apressure from about 100 psig (689 kPa gauge) to about 2000 psig (13790kPa gauge), a maximum catalyst temperature from about 350° F. (177° C.)to about 850° F. (454° C.) and a hydrogen circulation rate from about200 SCFB (35.6 std m³ /m³) to about 10,000 SCFB (1778 std m³ /m³). 18.The process of claim 14 wherein said hydrogenation catalyst comprises arefractory inorganic oxide and at least one metallic compound havinghydrogenation activity.
 19. The process of claim 18 wherein saidmetallic compound is selected from the metals of Groups VI-B and VIII ofthe Periodic Table.
 20. The process of claim 14 wherein said aqueousscrubbing solution comprises an alkaline compound.
 21. The process ofclaim 20 wherein said alkaline compound is sodium hydroxide, potassiumhydroxide or calcium hydroxide.
 22. The process of claim 14 wherein saidadsorbent is silica gel, activated carbon, activated alumina,silica-alumina gel, clay, molecular sieves or admixtures thereof. 23.The process of claim 14 wherein said contacting conducted in step (a) isperformed at conditions which include a pressure from about atmosphericto about 1500 psig (10342 kPa gauge) and a temperature from about 32° F.(0° C.) to about 300° F. (149° C.) and a liquid hourly space velocityfrom about 0.1 hr⁻¹ to about 500 hr⁻¹.
 24. The process of claim 14wherein the adsorbent regeneration conducted in step (b) is performed atconditions which include a pressure from about atmospheric to about 1500psig (10342 kPa gauge) and a temperature from about 32° F. (0° C.) toabout 300° F. (149° C.).
 25. The process of claim 14 wherein saidaqueous stream having a reduced hydrocarbonaceous compound concentrationis essentially hydrocarbon-free.
 26. The process of claim 14 whereinsaid elution solvent is naphtha, kerosene, diesel fuel, gas oil ormixtures thereof.